As fluid control valves that, when an actuator such as a fluid pressure cylinder is driven, control the flow rate, pressure, etc. of a pressure fluid supplied to or discharged from the actuator, fluid control valves having various configurations are known as disclosed in, for example, Patent Literatures, PTL 1 and PTL 2.
This type of fluid control valve is configured so as to have various functions according to the purpose of use as a fluid control valve that performs meter-in type control in which the flow rate at the time of supplying air is restricted and the flow rate at the time of discharging air is not restricted, a fluid control valve that performs meter-out type control in which the flow rate at the time of supplying air is not restricted and the flow rate at the time of discharging air is restricted, a fluid control valve that performs rapid discharge at the time of discharging air to prevent the operation delay, etc. usually by combining a needle valve that restricts the flow rate or pressure of the pressure fluid by narrowing the flow path, a flow rate control valve that opens and closes the flow path by interaction between the fluid pressure and the spring force, a check valve that allows the pressure fluid to flow only in one direction, etc.
However, in the foregoing conventional fluid control valves, the needle valve, the flow rate control valve, the check valve, etc. are separately incorporated in the valve housing, so that many of them are complicated in structure and large in size, and there is a problem that they are inconvenient for adjustment and handling and are not user-friendly. The advent of a fluid control valve that is further reduced in size and user-friendly has been desired.
Therefore, as disclosed in Patent Literature, PTL 3, the applicant of the present invention proposed a fluid control valve in which the function of the needle valve and the function of the flow rate control valve are, in a unified state, incorporated coaxially into the valve housing and that, compared with the conventional fluid control valves, is simple in structure, small in size, and user-friendly and has a rational design structure.
However, when this fluid control valve is used for applications in which the fluid pressure actuator is required to have higher responsiveness than usual, in order to prevent operation delay of the fluid pressure actuator from, it is necessary to further improve the fluid control capability of the fluid control valve.